Field of the Invention
The present invention relates to an imprint apparatus that forms a pattern of an imprint material on a substrate-side pattern region of a substrate using a mold, a related imprint method, and an article manufacturing method using imprint the method.
Description of the Related Art
As the demand for microfabrication of semiconductor devices or MEMS increases, not only has conventional photolithography technology, but also, microfabrication technology, in which an uncured resin on a substrate is molded by a mold to thereby form a resin pattern on the substrate, been receiving attention. This technology is also referred to as an “imprint technology”, by which a fine structure with dimensions of a few nanometers can be formed on a substrate. One example of imprint technologies includes a photo-curing method. An imprint apparatus employing the photo-curing method first applies an ultraviolet curable resin (imprint material, photocurable resin) to a shot region (imprint region) on a substrate (wafer). Next, the resin (uncured resin) is molded by a mold. After the ultraviolet curable resin is irradiated with ultraviolet light for curing, the cured resin is released from the mold, whereby a resin pattern is formed on the substrate.
Here, in a series of device manufacturing steps, heat processing in a film formation step, such as sputtering, is performed on a substrate to be subjected to imprint processing. Consequently, the entire substrate may be expanded or reduced, resulting in a change in the shape (or size) of the pattern region in the direction of two orthogonal in-plane axes. Thus, in an imprint apparatus, the shape of the pattern region (substrate-side pattern region) pre-formed on a substrate needs to be matched with the shape of the pattern region formed on a mold when the mold is pressed against the resin on the substrate. As a technique for making the shape of a substrate-side pattern region, which is slightly deformed, match the shape of the pattern region formed on a mold, Japanese Patent Laid-Open No. 2008-504141 discloses an apparatus that deforms a mold (pattern region) by imparting an external force to the outer periphery of the mold. In the apparatus disclosed in Japanese Patent Laid-Open No. 2008-504141, however, if the material used for the mold is quartz, the mold has a Poisson's ratio of 0.16 and, thus, if one end of the mold is pressed in the axial direction of the mold, the other end of the mold is expanded in a direction orthogonal to the axis. Thus, if such deformation occurs according to the Poisson's ratio of the mold, the plane of the mold is not easily deformed linearly, when it is desired that the mold is particularly deformed into a trapezoidal shape, resulting in adverse effects on superposition accuracy. Accordingly, as a method for preventing the mold from being deformed depending on the Poisson's ratio thereof upon such shape correction, WO 2009/153925 discloses an imprint method that makes the shape of a substrate-side pattern region match the shape of the pattern region formed on a mold by heat-deforming the mold.
If the material used for the mold is quartz, however, the thermal expansion coefficient of quartz is 0.51 ppm, whereas the thermal expansion coefficient of silicon, which is the material used for the substrate, is 2.4 ppm. The thermal expansion coefficients of the mold and the substrate differ by an order of magnitude. Thus, in the method disclosed in WO 2009/153925, the heat is transferred from the mold subjected to thermal deformation to the substrate, from the instant that the mold is pressed against the pattern formed on the substrate. Since the surface of the substrate having a relatively large thermal expansion coefficient may be largely deformed due to the heat, it is difficult to suppress adverse effects on superposition accuracy.